1. Field of the Invention
This invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device including an improved process of manufacturing a gate electrode of a MIS-FET for use, for example, in an LSI.
2. Background Art
In general, as shown in FIG. 9A, a method of manufacturing a MOSFET includes forming an N-well region 202 and a P-well region 203 in a silicon substrate 201 (e.g., S. B. Samavedam et al., IEDM Technical digest, 2002, p. 433).
Next, as shown in FIG. 9B, a HfO2 film 204 is deposited thereon as a gate insulating film. TiN 205 is deposited as a first gate electrode material and a silicon oxide film 206 is deposited as an etch mask material. A resist mask 207 is formed by using a P-well mask. As shown in FIG. 10A, the silicon oxide film on the NMIS region is removed to form a silicon oxide film hard mask 206A.
Next, as shown in FIG. 10B, the exposed TiN is removed by wet etching. As shown in FIG. 10C, the silicon oxide film hard mask 206A is removed using HF. A TaSiN film 208 is deposited as a second gate electrode material on the entire surface of the wafer. Further thereon, a poly-Si film 209 is deposited on the entire surface of the wafer.
Subsequently, although not shown in Samavedam et al., conventional processes are used to produce a MIS-FET by patterning a gate electrode, forming an extension, gate sidewall, and source/drain, and forming interconnection.
In a MIS-FET manufactured by the above method, different kinds of metal gates can be formed in the NMOS and PMOS regions on the substrate surface. However, since the hard mask is formed from a silicon oxide film, its removal requires etching with HF-containing liquid. In this situation, while HfO2 having nearly normal composition is unlikely to be etched, a SiO2-based or HfSiOx-based gate insulating film will be etched by HF. Therefore the above method is not applicable.
As described above, in the conventional method, since the hard mask is formed from a silicon oxide film, its removal requires etching with HF-containing liquid. In this situation, there is a problem that the above method is not applicable because a SiO2-based or HfSiOx-based gate insulating film will be etched by HF.